object SetDemo {
  def main(arg: Array[String]): Unit = {
    var members = Set("张三","李四","王五")
    members += "李四"
    members += "赵六"
    println("志愿者社团成员:")
    for (member <- members){
      println("- " + member)
    }
    val hasZhangsan = members.contains("张三")
    println(s"是否有张三? $hasZhangsan")
    println(s"实际成员数:${members.size}")
  }
}
